Cardiovascular

• Functions of the Circulatory System

  • Transportation (respiratory gases, nutrients, and wastes)
  • Regulation (hormonal and temperature)
  • Protection (clotting and immunity)
• Major Components of the Circulatory System

  • Cardiovascular system (heart, blood vessels)
  • Lymphatic system (lymphatic vessels, lymphoid tissues, lymphatic organs)
• Arterial blood


  Leaving the heart, bright red, oxygenated (except for blood going to the lungs)
• Venous blood


  Entering the heart, dark red, deoxygenated (except for blood coming from the lungs)
• Blood composition


  45% formed elements, 55% plasma (by volume)
• Constituents of blood


  • Plasma
  • Formed elements
• Plasma


  Fluid part of blood, contains water and dissolved solutes
• Plasma proteins


  • Albumin (creates osmotic pressure)
  • Globulins (transport lipids and fat-soluble vitamins, antibodies)
  • Fibrinogen (helps in clotting)
• Plasma volume regulation


  Osmoreceptors in the hypothalamus cause the release of ADH from the posterior pituitary gland if fluid is lost
• Erythrocytes (red blood cells - RBCs)

  Flattened, biconcave discs, carry oxygen, lack nuclei and mitochondria, have a 120-day life span, each contain about 280 million hemoglobin molecules
• Anemia


  Abnormally low hemoglobin or RBC count
• Leukocytes (white blood cells - WBCs)


  Have nuclei and mitochondria, move in amoeboid fashion, diapedesis (movement through capillary wall into connective tissue)
• Types of leukocytes


  • Granular leukocytes (neutrophils, eosinophils, basophils)
  • Agranular leukocytes (monocytes, lymphocytes)
• Platelets (thrombocytes)


  Smallest formed element, fragments of large cells called megakaryocytic, lack nuclei, very short-lived (5-9 days), clot blood with several other chemicals and fibrinogen, release serotonin that stimulates vasoconstriction
• Hematopoiesis (hemopoiesis)


  1. Hematopoietic stem cells give rise to all blood cells

  2. Process occurs in myeloid tissue (red bone marrow) and lymphoid tissue

  3. As cells differentiate, they develop membrane receptors for chemical signals
• Erythropoiesis


  1. Formation of red blood cells

  2. Red bone marrow produces about 2.5 million RBCs/sec

  3. Process stimulated by erythropoietin from the kidneys that respond to low blood O2 levels

  4. Process takes about 3 days
• Hematocrit (Hct) Test


  Measures the percentage of red blood cells in the blood
• Leukopoiesis


  1. Formation of white blood cells

  2. Cytokines stimulate the production of the different subtypes
• ABO system


  Antigens on erythrocyte cell surfaces (Type A has A antigen, Type B has B antigen, Type AB has both A and B antigens, Type O has neither A nor B antigen)
• Plasma antibodies in ABO system

  Type A has anti-B antibodies, Type B has anti-A antibodies, Type AB has no antibodies (universal recipient), Type O has anti-A and anti-B antibodies (universal donor)
• Rh system


  Rh-positive blood has Rh factor antigen present in RBCs, Rh-negative blood has no Rh factor present in RBCs and no anti-Rh antibodies present naturally in plasma
• Erythroblastosis fetalis


  Hemolytic anemia that may occur when the blood types of a mother and baby are incompatible, more likely to occur during a second or subsequent pregnancy, or following a miscarriage or abortion
• All Rh-negative mothers who carry an Rh-positive baby should be treated with an immunoglobulin (antibody) serum (RhoGAM)
• A person with Rh-negative blood who receives a transfusion of Rh-positive blood will also develop anti-Rh antibodies and be at risk of an immune reaction if exposed to Rh-positive blood again later
• Combined ABO-Rh system


  Both the ABO and Rh systems are often used in combination to identify a person's blood type
• Intact endothelium


  Secretes prostacyclin and nitric oxide, which vasodilate and inhibit platelet aggregation, and CD39 (vascular nucleoside), which inhibit platelet aggregation further
• Blood clotting


  1. Clotting factors released at the injury site produce prothrombin activator

  2. Prothrombin activator and calcium convert prothrombin to thrombin

  3. Thrombin reacts with fibrinogen and triggers formation of fibrin, which traps RBCs to form a clot
• Thrombus


  When a clot stays in the place it has formed, condition is called thrombosis
• Embolus


  When a part of a clot dislodges and circulates through the bloodstream, condition is called embolism
• Plasmin


  Digests fibrin, dissolving blood clots
• Drugs that can prevent clotting or coagulation

  • Calcium chelators (sodium citrate or EDTA)
  • Heparin (blocks thrombin)
  • Coumadin (inhibits vitamin K)